This invention relates to a pulse combustor, and more particularly to an improvement in a flame trap which is provided at the inlet of a combustion chamber through which a mixture of air and fuel gas is supplied into the combustion chamber.
A pulse combustor is well known in the art in which a mixture of air and fuel gas is supplied to a combustion chamber, where it is subjected to an explosive combustion in a pulse mode.
FIG. 6 is a sectional view showing an complete pulse combustor, and FIG. 7 is an enlarged sectional view showing the essential components of the pulse combustor.
The pulse combustor 31 has a flame trap 34 between a combustion chamber 32 and a mixing chamber 33. In the mixing chamber 33, fuel gas introduced through a gas pipe 35 and a gas chamber 36 is mixed with air introduced through an air blower 37 and an air supply chamber 38. The mixture of air and fuel gas is supplied into the combustion chamber 32 through a number of vent holes 39 (hereinafter referred to as "cells 39", when applicable) formed in the flame trap 34. In the combustion chamber 32, the mixture is explosively burned into combustion gas. The combustion gas is sent to a tail pipe (not shown) through a discharge outlet 40 coupled to the combustion chamber 32. In this operation, a negative pressure is developed in the combustion chamber 32 so that a successive mixture of air and fuel gas is introduced into the combustion chamber 32 through the cells 39 formed in the flame trap 34, and is explosively burned by the return flame from the tail pipe (not shown).
The flame trap 34 of the pulse combustor is generally as shown in FIG. 8. That is, the flame trap 34 is made of a heat-resistant porous plate made of ceramic material. The flame trap 34 has a number of cells 41 arranged like the holes of a grating.
The flame trap made of a porous plate of ceramic material as shown in FIG. 8 has the following problems: In manufacturing the flame trap, it is not possible to reduce the thickness of the ceramic walls between the cells 41 beyond a prescribed limit. The purpose of the flame trap is not only to straighten the stream of the mixture flowing into the combustion chamber but also to prevent the flow of back fire from the combustion chamber toward the mixing chamber. Hence, each of the cells 41 should be small in aperture area. However, if the aperture area is made small the numerical aperture is unavoidably as required, then the numerical aperture is unavoidably decreased. Because of limitations involved in manufacturing is considerably difficult to make the numerical aperture higher than 70%.
Accordingly, during combustion, the flame trap is low in back-fire preventing ability, and the combustibility (CO/CO.sub.2 ratio) is also low. Thus, the flame trap of this type adversely affects the performance of the pulse 10 combustor. This fact obstructs the high load combustion of the pulse combustor, and accordingly the miniaturization of the latter.
The flame trap of ceramic material is readily broken by shock. Hence, during assembly, the flame trap may be broken when struck by other components, or its fragments may clog up the vent holes. That is, the flame trap may be one of the factors which impedes the assembling work of the pulse combustor.